fix: Fixing a crash when attempting to call finishWriting

[ruisebas]

Issue #, if available:

• Crash - FaceLivenessDetectionViewModel.sendFinalVideoEvent() #148

Description of changes:

This PR attempts to fix an NSInternalInconsistencyException crash that might be happening when calling AVAssetWriter.finishWriting on an instance that is already completed.

There was a previous validation in place that checked if state != .complete, but state is a local variable that is not really tracking the write's state, so I decided to replace it with AVAssetWriter.status.

Check points: (check or cross out if not relevant)

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 30.48%. Comparing base (da7f9fa) to head (4d96c38).
Report is 3 commits behind head on main.

Files	Patch %	Lines
Sources/FaceLiveness/AV/VideoChunker.swift	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #161   +/-   ##
=======================================
  Coverage   30.48%   30.48%           
=======================================
  Files          57       57           
  Lines        2227     2227           
=======================================
  Hits          679      679           
  Misses       1548     1548           

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